The present invention relates to a method and a device for controlling the number of pumps to be operated at any given time in a multi-pump pumping system, such as a water supply system, a sewer system, an irrigation system, a drain system, or the like.
In an irrigation system for supplying irrigation water to farms, for example, after the irrigation water is pumped-up into a pond by one or more pumps in the system, it is supplied to various outlets to the farms. In such system, it is generally desirable to regulate the pumping-up flow rate by suitable control of the pumps in the system to provide maximum economy of operation with a simple construction. There is hitherto well known a multi-pump system which controls the pumping-up flow rate by changing the number of pumps which are operated at any given time in response to the detected water level of the pond. That is, in this known system, the operation of the respective pumps is controlled in response to whether or not the actual water level of the pond is between the upper limits and the lower limits of the water levels which are capable of being maintained by the respective pumps.
Furthermore, there is hitherto known a program control system which changes the number of the pumps being operated in response to a predicted load flow rate. However, these prior art systems cannot provide the degree of optimum pump operation which makes it possible to control the pumping-up flow rate with the small number of switching or change-over operations of the pumps necessary to achieve low energy consumption in the system.